384 Tlie American ( r eol og ! xt . D.-cember, xma 
linii'stonc. 'JMius tlic fauiuis of tlic l)e\oni:iu uiul ('arl)onifer- 
oiis of tlu' upper Mississippi valley become more sharply con- 
trasted than ever. And the apparent mingling of faunas from 
the two geological s^^stems manifestly' is due to erroneous as- 
sumptions rather than detailed field evidence. 
Depriving the "Lithographic"' limestone, which attains a thick- 
ness of more than (JO feet at Louisiana, in Pike count}', Missouri, 
almost entirely of the extensive fauna commonly ascribed to it, 
and which has been seen comes from a thin seam lying below the 
calcareous layers, its geologic age becomes a problem yet to be 
solved. The few fossils known from the limestone itself have 
been heretofore rarel}- met with. But until abundant evidence to 
this etfect is found it seems advisable to still consider the 
Louisiana (Lithographic) limestone in this region as the basal 
member of the Carboniferous. 
It appears very probable that a marked unconformity exists be- 
tween the Carboniferous and Devonian rocks of the area under 
{•onsideration, instead of a regular sequence of strata as has been 
supposed usually. The proofs of this statement, however, are 
not such at present as to warrant a definite formulation of the 
evidence, yet man}- facts recentl}' observed point strongly towards 
this conclusion; while the sharply contrasted faunal peculiarities 
are in themselves very suggestive, and very remarkable. 
EDITORIAL COMMEI^T. 
TiiK First Dkcad ok tiik (Jkologist. 
AYith this month closes the tenth volume of Tiik American 
(tEologist. It may not Ije unwholesome to revert liriefly to the 
past five years. That time is too short an interval to warrant 
the expectation of great results, or to span any of the great 
epochs which mark revolutions in science. There is of course in 
the history of every revolution, whether in politics or in science, 
a seeding time and a reaping time. The changes in geologic 
science, however, have always been so gradual, and spread over 
so many countries, that the participants have rarely realized 
whether they were sowing or reaping; and it has required the 
observer of a later generation. Avho could gather up the elements 
